1. Field of the Invention
The invention relates to electric motors and is directed more particularly to an electric motor having a discrete plastic brush card mounted in an endframe but isolated from the endframe.
2. Description of the Prior Art
In electric motors, brushes are commonly retained in brush tubes which usually are molded integrally with the endframe of the motor. The endframe and brush tubes typically are of a plastic material. The brush tubes are square in cross-section and hollow, somewhat like elevator shafts, in which spring-biased brushes are slidably moveable into engagement with the commutator of the motor.
Noise usually is generated at the commutator-brush interface, the surface of the rotating commutators being continuously engaged by the relatively stationary brushes. The noise is exacerbated by the hollow elongated brush tubes, acting as echo-chambers, which, being integral with the endframe, transmit the noise to the endframe, which is exposed.
In some applications, the noise generated at the commutator-brush interface is unacceptable. For example, in D.C. motors used in automobiles for operation of power seats, it is most desirable that the motors operate silently.
Accordingly, there exists a need for a motor having a quieter arrangement of endframe and brush tubes.